1. Field
Aspects of the present invention relate to an organic light-emitting display apparatus and a method of manufacturing the same, and more particularly, to an organic light-emitting display apparatus having improved luminescent properties.
2. Description of the Related Art
In recent years, conventional display apparatuses have been replaced by portable, thin, flat panel display apparatuses. Among flat panel display apparatuses, organic or inorganic light-emitting display apparatuses, which are self-emitting display apparatuses, have advantages, such as a wide viewing angle, a high contrast, and a rapid response speed, and thus, have been spotlighted as the next generation display apparatuses. In particular, organic light-emitting display apparatuses, including a light-emitting layer formed of an organic material, have a better brightness, a lower driving voltage, and a higher response speed than inorganic light-emitting display apparatuses.
An organic light-emitting display apparatus includes an organic emissive device having a cathode and anode placed in conjunction with an organic emissive layer. When a voltage is applied between the cathode and the anode, visible light is produced by the organic emissive layer. Since electric charges are supplied to the organic emissive layer, via the cathode and the anode, the contact between the organic emissive layer and the cathode or the anode affects the optical properties of organic light-emitting display apparatus.
An organic light-emitting display apparatus includes a pixel definition layer, that is, an insulating layer defining sub-pixels. An opening is formed in the pixel definition layer, thereby exposing an electrode, and an organic emissive layer is formed on the electrode. In this case, a bent portion of the electrode may not contact the organic emissive layer, due to the depth of the opening.
When the portion of the organic emissive layer is spaced apart from the electrode, rather than contacting the electrode, light is abnormally emitted, or is not emitted, at the portion. Due to the abnormal portion, the luminescent properties of sub-pixels cannot be regularly realized. As a result, there is a limit in improving the luminescent properties of the organic light-emitting display apparatus.
In addition, the luminescent properties of the organic light-emitting display apparatus can deteriorate at a bent portion of the organic emissive layer. Also, the organic emissive layer may contact a lower electrode. In this case, if an edge of the lower electrode has poor surface properties, an electric field is concentrated on the edge, thereby partially deteriorating a device and reducing the lifetime of the organic light-emitting display apparatus.
Conventionally, a pixel definition layer is formed of an insulating material and is disposed on a first electrode, in order to define sub-pixels. An opening, through which the first electrode is exposed, is formed in the pixel definition layer. The intermediate layer including the organic emissive layer is formed on the first electrode and is exposed through the opening. In this case, the intermediate layer is bent, due to the height of the pixel definition layer and the shape of the opening.
In addition, due to an organic material of the intermediate layer, since it is not easy to uniformly form the intermediate layer as a thin film, the intermediate layer cannot be sufficiently formed on the pixel definition layer and the opening, thereby creating a vacancy. Besides, a portion of the intermediate layer may not contact the first electrode. Generally, this problem occurs in edge portions of a sub-pixel. In particular, when the intermediate layer is formed using heat transference, since an interval between a donor film and the first electrode is increased, when the height of the pixel definition layer is increased, it is not easy to sufficiently transfer the intermediate layer onto the first electrode. As a result, some portions of the intermediate layer may contact the first electrode.
During operation of the organic light-emitting display apparatus, an electric field is concentrated on a portion of the intermediate layer, which corresponds to an upper portion of the edge of the first electrode. This is because an electric field is concentrated on the edge of the first electrode. This is because a portion of the first electrode, which corresponds to the hole, is bent, thereby generating sharp edges. Thus, an electric field is concentrated on the sharp edges.
In this case, the portion of the intermediate layer deteriorates where an electric field is concentrated deteriorates, which also affects a normal central portion of the intermediate layer, thereby reducing the luminescent properties of the sub-pixels. As a result, the overall luminescent properties of the organic light-emitting display apparatus deteriorate, and the lifetime of the organic light-emitting display apparatus is reduced.
In particular, when the first electrode includes a conductive material is formed in a predetermined pattern, photolithography, or the like is used. In this case, the edge of the first electrode has poor surface properties. That is, surfaces of the some portions of the first electrode are eroded or fractured. In this regard, it is easier for an electric field to be concentrated on such surfaces.
A portion of the first electrode is bent, thereby generating the sharp edges. Thus, it is easier for an electric field to be concentrated on such portions. Thus, an electric field is easily concentrated on the portion of the intermediate layer, which corresponds to the upper portion of the edge of the first electrode, and thus, it is easy for the portion of the intermediate layer to deteriorate, thereby reducing the luminescent properties of the organic light-emitting display apparatus.